Bacterial and Viral Diseases

Poultry diagnostic laboratories are located throughout Florida to assist in the diagnosis of poultry diseases (see A Guide to Commercial Poultry Production in Florida). A brief description of the more common diseases is provided to familiarize county Extension personnel with these diseases.


Cause: A virus.
Transmission: Mosquitoes are considered an important means of transmission.
Lesions: Wart-like nodules covered with brown scabs on the bare parts of the head, feet and around the vent. Yellowish cheese-like areas may occur on the inside of the mouth.
Treatment: None.
Control: All birds intended for laying purposes should be vaccinated. Birds whose resistance has been weakened through any condition or disease should not be vaccinated until they are healthy.


Cause: Simple coryza, the common cold, is usually caused by improper management in which birds are subjected to undue exposure. Infectious coryza is caused by a specific microorganism and its severity is increased in birds subjected to resistance lowering factors.
Symptoms: Respiratory distress accompanied by watery and swollen eyes and unthrifty condition.
Treatment: Simple coryza responds to correction of undue exposure. Antibiotics are beneficial. Infectious coryza sometimes responds to erthyromycin, streptomycin and sulfonamides if treated early.
Control: Depopulation of farms and starting with clean chicks. Consider vaccination if exposure risk is high.


Cause: A virus.
Symptoms: A disease affecting chickens clinically under 6 weeks of age. Incoordination of gait, staggering, falling to one side, occasional tremors of the head. Excitement intensifies symptoms.
Treatment and Control: No treatment except isolation of affected birds. Vaccinate breeder flocks to provide immunity to chicks.


Cause: A bacterial organism, Pasteurella Multocida.
Symptoms: Sudden death, greenish diarrhea, high temperature, comb and wattle purple. Also swollen wattle. A chronic form of the disease exists in which lesions localize in a joint, wattle, infraohits (Author Note), sinuses or other tissue.
Treatment: Many drugs are available.
Control: Improve sanitation. Depopulate and use one age bird on farms. Bacterins may be used to aid prevention.


Cause: A virus.
Symptoms: Respiratory distress, sneezing and rattling. In laying birds, a drop in egg production, misshaped eggs with low quality. Some strains of the virus may cause severe kidney damage.
Treatment: None.
Control: Vaccination.


Cause: A virus of the leukosis-sarcoma complex. Occurs mainly in laying hens between 4 and 10 months or age.
Symptoms: Tumors in the bursa of Fabricius will spread to many other internal organs, especially the liver, spleen and kidney.
Treatment: None.
Control: Development of resistant strains of chickens by Poultry geneticists.


Cause: A herpes-virus. Occurs mainly in chickens under 16 weeks of age. Symptoms: Leg and/or wing paralysis, high mortality, tumors on visceral organs.
Treatment: None.
Control: Vaccination of chicks at one day of age.


Cause: A virus.
Symptoms: Respiratory distress, and rasping followed in 1 or 2 days by a paralysis of legs and wings and bad down between legs or straight back over shoulders, twisting of neck (stargazing). In adult birds, loss of production along with some respiratory distress and paralysis after 4 to 6 days.
Treatment: None.
Control: Vaccination.


Cause: A virus. Highly infectious, severity varies.
Symptoms: Sudden death is common. Clinical signs include sudden drop in egg production. depression, loss of appetite, blue combs and wattles, diarrhea, blood-tinged discharge from nostrils.
Treatment: None.
Control: Monitoring, strict quarantine and rapid destruction of all infected flocks. Poultry producers should practice strict management control.

* From Diseases of Poultry, a paper by Dr. Gary D. Butcher, DVM, PhD., Poultry Veterinarian, College of Veterinary Medicine, Institute of Food and Agricultural Sciences, University of Florida, Gainesville. From publication PS-5, Florida Cooperative Extension Service. .

Back to the Main Health Page

Copyright 1995-2004 by Dennis Hawkins, All Rights Reserved.